Generally, the industry of semiconductor manufacturing involves highly complex techniques for fabricating integrating circuits using semiconductor materials which are layered and patterned onto a substrate, such as silicon. Due to the large scale of circuit integration and the decreasing size of semiconductor devices, the fabricated devices have become increasingly sensitive to defects. That is, defects which cause faults in the device are becoming increasingly smaller. Each device needs to be fault free prior to shipment to the end users or customers.
Various inspection systems are used within the semiconductor industry to detect defects on a semiconductor reticle or wafer. Some conventional optical inspection tools locate defects on patterned wafers by scanning the surface of the wafer with a tightly focused laser spot and measuring the amount of light scattered by the illuminated spot on the wafer. Dissimilarities in the scattering intensity between similar locations in adjacent dies are recorded as potential defect sites.
Some conventional scanning systems include an illumination system one or more incident beam sources for deflecting one or more beams across the wafer. The scanning system may specifically include an acousto-optic deflectors (AOD's) and a mechanism for controlling the AOD's deflection characteristics. For instance, a clock may be used to generate a “chirp” signal input to each AOD.
It would be beneficial to provide improved inspection systems having deflectors, such as AOD's.